Synchronous motor device



Oct. 1., 1957 M. MORRISON 2,303,551

SYNCHRONOUS MOTOR DEVICE Original Filed Oct. 16, 1952 2 Sheets-Sheet 1man i q m,6-

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Fla. 1. WWWW Oct. 1, 1957 M. MORRISON SYNCHRONOUS MOTOR DEVICE OriginalFiled Oct. 16, 1952 2 Sheets-Sheet 2 THIS AREA REPRESE/VTS A/V ORGAlV/ZA T ION LIKE 7' HA 7' SHOW/V IN DOTTED AREA "8" THIS AREA REPRESENTSAN ORGANIZATION LIKE THAT SHOWN //v DOTTED AREA '14" INVENTOR.

United States Patent SYNCHRONOUS MOTOR DEVICE Montford Morrison,Rochester, N. Y.

Original application October 16, 1952, Serial No. 1314,99 1. Divided andthis application February 3, 1954, Serial No. 407,851

Claims. 01. 318-47) The present invention generally relates toelectrical means and methods of indicating frequency rates of variationsin electrical circuits, it more specifically relates to such methodswhere pulses of any physical nature may be transduced into electriccurrent and as a specific application it may be employed in theelectrical determina tion of watch rates.

The present application is a division of application Serial No. 314,991,filed October 16, 1952, now abandoned.

Among the general objects of the invention is to provide a supersensitive means and method of determining the relative speeds ofrevolving shafts and the application of such means and method to themeasurement of recurrent energy pulsations or variations.

A specific such application is that of measuring small changes in thefrequency of alternating current generators.

A further specific application is to the indication of minute changes inthe frequency of watch and clock rates.

The vast majority of American watches tick at a rate of five per secondand the difliculty of attaining an electrical method and means ofraising this five cycle impulse frequency to a frequency rate which ismeasurable with electrical instruments is exceedingly difiicult andexpensive because of the high electrical Q involved in the process.

In the present invention instead of depending upon a high electrical Q,a novel device substituting mechanical means is employed. Among theobjectives of the invention is to provide means for convertingrelatively low rate per second impulses, such as those produced by watchticks, into relatively high revolutions per second motor devices, whichcan be utilized at these relatively high revolving speeds toeconomically measure the rate of the relatively low rate impulses,without the introduction of what is known in such methods as jittering.That is, in the process of controlling a relatively high frequencycurrent by means of a relatively low frequency impulse, there is aninterval during which, the low frequency impulse does not control thehigher frequency. During this interval the higher frequency system,tends to, drift in frequency in one direction. or the other, such thatwhen controlling impulse is injected into the circuit, the startingpoint of the higher frequency systemis suddenly changed so that thechange in thishigher frequency is said to jitter back or forth at, thefrequency of the impulse rate.

In the present invention a low frequency pulse is injected for eachcycle and therefore fixes the average frequency rate for each cycle andthe tie in between the average frequency rate and the high frequency orhigh speed rate is continuous and therefore cannot jitter.

In the present invention the relatively low pulse frequency of, forexample, a watch ticking at rate of approximated five times per second,is converted into an alternating current of five cycles per second, andthis Patented Oct. 1, 1957 five cycle alternating current is caused tocontrol the speed of an electric motor driven from an independentsource, and which motor provides energy for the indication desired.

To follow such a plan of frequency measurement, the driving motor speedmust be synchronous with the five cycle frequency, because the making of-a five cycle synchronous electric driving motor presents problems tootremendous and too extensively complex for practical application tofrequency measurement.

Further the shaft speed of a five cycle synchronous motor cannot exceed300 revolutions per minute, and such a shaft speed is not as well suitedto speed measurement by electrical or electromagnetic means as highershaft speeds, as will be obvious from this specification hereinafterrecited, because of the larger and heavier parts required for low shaftspeed electrical indications.

A further object of the invention is to provide a synchronizable motorcombination in which the main driving torque for the combination isobtained from a source of electric current independent of the source ofelectric current which fixes the synchronous rotation of thecombination.

The applicant is aware of prior art synchronous motor combinations, inwhich two motors, or their equivalent, are employed to attainsynchronous operation from a single source of alternating current, butthe operation of these combinations depend upon a single shaft speed anda common source of alternating current for both motor fields, a firstmotor field providing an accelerating torque which brings the shaftspeed up to a value which approaches synchronous speed and then a secondmotor synchronous field takes over the load and provides all the torquefor synchronous operation. The first motor field then acts merely as adamper winding against motor hunting and provides no shaft torque in theabsence of hunting.

In the present invention there is no necessary relation betweenfrequencies which may be employed in the two motor combination. Toacquire a relatively high shaft speed operating at a fixed multiplefrequency of the five cycle per second order, a relatively high speedmotor having preferably a low rate of change in its speed torquecharacter in the neighborhood of its loaded operating speed is employed,so that a relatively small amount of added or subtracted torque to themotor shaft will serve to cause it operated at a speed fixed by theadded or subtracted torque.

By this means and method a relatively small highspeed high-torque motorby mechanical gearing can be caused to operate at a synchronous multipleshaft speed of a comparatively small low torque synchronous motor.

Further by this means and method the energy required to fix thefrequency of shaft revolutions to be measured, is a comparatively smallfraction of the total energy required for the speed or frequencyindication, where the indication is determined by shaft speed.

Having recited some of the objects of the invention, the applicant willnow describe several specific embodiments thereof, from which the natureof the invention may be clearly drawn.

The invention will be more fully understood in its'structuralcharacteristics from the following description when read in connectionwith the accompanying drawings, of

Fig. 3 shows a circuit organization employing the mechanism of Figs. 1and 2 to complete an embodiment of the invention.

In Fig. 1, 1 and 2 are identical motors of an asynchronous type andwhile the motors employed in the positions indicated may be driveneither from direct current or alternating current, and the principalrequirement of these motors is that they have a continuous torque suchas found in miniature induction alternating current motors and in directcurrent commutator motors.

The motors as illustrated in Fig. 1 are squirrel cage induction motorswith shaded pole windings and have a no load speed of about 3350revolutions per minute, but this speed reduces to about 3050 under theload hereinafter described.

The torque of these motors is not sensitive to line voltage variationand is smoothly continuous down to about 2800 revolutions per minute.

The shafts of these motors are identified by 3 and 4 and the statorcoils by 5 and 6.

The electrical connections of stator coil 5 are represented by 7 and 8and the electrical connections to stator coil 6 are represented by 9 and10.

The numerals above employed appear on the same parts in Fig. 2. In Fig.l, 11 and 12 are identical motors, but of a synchronous type. The motors11 and 12 differ from motors 1 and 2 in that the rotors of the highernumbered motors are constructed for synchronous operation. These motorsmay be of the hysteresis type, the squirrel cage salient pole reactiontype (sometimes erroneously referred to as hysteresis motors) or theymay be of the type preferred by the applicant, which is of the constantmagnetic field rotor type. r

In the present embodiment the actual motors employed in the embodimentshown have the same stator laminations for the synchronous type asemployed in the asynchronous type. The synchronous type motor has theshading coil windings removed from the stator pole faces and a solidcompletely cylindrical rotor highly permanently magnetized throughoutthe direction of some diameter of the cylinder.

Such a motor has a much higher electrical output, for the alternatingcurrent input of the field coils 13 and 14, than is attainable with thesame electrical input in either an hysteresis type of motor or in asquirrel cage salient pole rotor reaction type.

Motors 1 and 2 having power output rating of .0015 1-1. P. and motors 11and 12 are built in motor frames hav- 1ng an output rating of .002 H.P., but these output rates are measured at 60 cycles and the synchronousrating of motors 11 and 12 at the frequency used in connection withthese motors is a small fraction of this amount.

Electrical connections for stator coil 13 are represented by 15 and 16and electrical connections for stator coil 14 are represented by 17 and18.

On rotor shaft 3 of motor 1 is fixed a pinion 19 and on rotor shaft 4 ofmotor 2 is fixed a small pinion 20. Pinions 19 and 2%} are 13 tooth 64pitch steel pinions.

Specific numerical values are given in this specification to moreclearly fix the size and proportion of the parts employed, and as amatter of fact the parts and elements shown in Figs. 1 and 2 are fullsize in the original patent drawings.

In Fig. 2 on to an extension of shaft 3 is a hub 21 and on extension ofshaft 4 is a similar hub 22. Hubs 21 and 22 carry copper disks 23 and24- such as employed in eddy current brakes and eddy current motors. Asa matter of fact the rotation of these disks hereinafter more fullydescribed, comprise the moving parts of eddy current motors.

The corresponding parts described in Fig. 2 will be identified in Fig. lby the corresponding numerals.

Figs. 1 and 2, 25 is a shaft journaled in ball bearings 26 and 27. Thesebearings may be knife edged bearings, if and when desired. Shaft 25carried fixed to it a hal- 4 ance beam structure 28. The beam structure28 comprises a two air-gap permanent field source of magnetic fluxhaving one or more permanent magnets employed in its structure.

In the embodiment shown, beam 28 has an identical beam member 29 and isseparated by hollow cylindrical permanent magnet 30. Solid cylinders 31and 32 are fixed to beam 28 and identical solid cylinders 33 and 34 arefixed to beam member 29. Solid cylinders 31, 32, 33 and 34 may bepermanent magnets or materials having just good magnetic permeability.

Obviously if five permanent magnets are employed to create the fluxfield in the beam structure, stronger magnetic fields are attainable andmay be so employed if and when desired.

Those skilled in the art will appreciate that with beam members 28 and29 of magnetically high permeability material and the permanent magnetor magnets properly arranged, the magnetic flux field will follow thedotted lines illustrated in Fig. 2 and one magnetic flux air-gap iscreated between solid cylinders 31 and 33 and a second magnetic fiuxair-gap is created between solid cylinders 32 and 34.

At this point it is believed advantageous to call attention to the factthat the rotation of disk 23 through magnetic flux field whichpenetrates it, causes balance beam 28 to be angularly displaced alongthe direction of the rotation of the disk at the area at which themagnetic field flux penetrates the disk. Likewise rotation of disk 24has the effect of rotating balance beam 28 in a similar way dependingupon the direction of rotation of the disk 24.

If disks 23 and 24 rotate in opposite directions and the balance beam 28is so adjusted along its horizontal axis that the magnetic drag causedbetween disks on the balance beam causes the pointer 35 to indicate zeroposition on scale 37, then any diiference in speed of disks 23 and 24will cause the pointer 35 to shift to the right or to the left and thescale can be calibrated by this shift to indicate the difference in thespeeds of shafts 3 and 4.

It must be clearly understood that the specific embodiment which isdescribed is only one way of embodying the invention and it must beclearly born in mind that disks 23 and 24 do not have to be of the samesize nor do they have to run at the same speed to give a balanced torqueon beam 28.

The torque on beam 28, as will be appreciated by those skilled in theart, depends also upon the relative strength of the magnetic fieldswhich penetrate the two disks as well as the distance of the air gapfields from the center of the rotating disks and also does it dependupon Whether the disks are made of the same material, the samethickness, or other minor variations well known in the art.

Such a magnetic balance of such a beam constitutes a supersensitivemeans of detecting minute differences in the speeds of the disks. Itwill be remembered that in similar structures employed in laboratoryweighing balances they can be easily made sensitive to a difference intorque of one milligram or even less. It is, of course, obvious to thoseskilled in the art that in such a balance beam as described in thisinvention the beam shaft 25 does not necessarily have to be locatedbetween the disks.

The beam shaft 25 is only located between rotating disks 23-and 24 whenthe disks rotate in opposite directions. However, if and when it isdesired to rotate the disks 23 and 24 in the same directions, themagnetic flux gaps would then be located on the same side of each diskand the center shaft 25 would be appropriately located between them.' Itis not believed that this structure is of sufiicient practicability towarrant a special figure in the drawings to disclose it and that themere mention of such a structure is sufliciently obvious to not requiremore description of it, for purposes of disclosure. 7

The structure described in the foregoing disclosures structure memberswhich provide a magnetic balance of beam pointer 35 when disks 23 and 24rotate in opposite directions and the location of shaft 25 flux strengthand other essential elements already described are taken intoconsideration and the pointer 35 indicates differences in speeds of thedisks 23 and 24.

The applicant will now describe how disks 23 and 24 are made to causethe pointer 35 to indicate transduced pulse rates, the frequency ofalternating currents and fre quency differences in general.

On shaft 37 and 38, Fig. 1, of synchronous motors 11, and 12 are fixedspur gears 39 and 40, Figs. 1 and 2. Spur gears 39. and 4.0 are 130tooth 64 pitch gears which are meshed with pinions 19 and 20 of motors 1and 2 so that asynchronous motors 1 and 2 drive synchronous motors 11and 12 in the present embodiment at the speed of motors 1 and 2.

The magnetic loading of disks 23 and 24 in their respective air-gaps,plus the loading of synchronous motors rotors of motors 11 and 12, causethe shaft speeds of motors 1 and 2 to reduce to about 3050 revolutionsper minute and the shaft speeds of synchronous motors 11 and 12 to bedriven at slightly. above 300 revolutions per minute, the gear ratiodescribed being 1 to 10.

The structural characteristics necessary to cause pointer 35 to indicatepulse rate frequencies or frequency differences, requires thatsynchronous motors 11 and 12 be tied in eletcrically to alternatingcurrent frequencies necessary to. accomplish the desired results.

In the present embodiment, which is concerned mainly for the purpose ofillustration with the measurement of frequency differences, it will beappreciated that if one two-.motor'unit drives one disk at astandardized predetermined number of revolutions per minute, that thepointer will indicate zero if and when the other set of motor units runsat the same speed, if they are so set to do and if not, when they areset to zero at equal magnetic drags on the balance beam. So that whenone motor unit is set in operation at a standardized frequency thepointer 35 indicates fast or slow depending upon the alternating currentfrequency feed to the other unit.

Application of the. structure above described to the measurement ofwatch rates is set forth in Fig. 3 which will now be discussed. In Fig.3 the electric motors described in Figs. 1 and 2 are shown with theirstators alone and without gears and other mechanism for the sake ofclearness. The numerals of Fig. 3 which are found in Figs. 1 and 2represent the same members and it is not thought necessary noradvantageous to re-describe members already described.

In Fig. 3 the organization contained in dotted area A represents aconventional impulse amplifier which is signal fed by microphone 41.

The organization shown in dotted area B represents a relaxation typeoscillator employing a gas tetrode or equivalent electronic dischargedevice, similar to those described in applicants Patent Numbers2,390,659 and 2,435,751.

It is believed that these two circuit organizations are sufficientlyconventional not to require any description of them. The ticks fromwatch 42 are amplified through the conventional amplifier contained indotted area A and the output of this amplifier is connected to thecontrol electrode of gas tetrode 43, which controls relaxationoscillator of the type shown in the dotted area B.

The starting time for each oscillation of relaxation oscillator B isinstituted by the amplification of the watch tick 42, but its sinusoidalcharacter is determined by the filter organization 44, the capacitor 45and the inductance which bridges the capacitor 45 in the bridge circuit46.

Area B in cooperation with its external shunt circuit 4.6. becomes, asource of alternating current having a 6 period corresponding to thefrequency determined by the ticks of watch 42. The period of saidalternating cur, rent is determined by the interval between the ticks ofthe watch and therefore is adjusted, if necessary, when the watch ratechanges to exactly represent the beat rate of the watch.

The external circuit 46 of the oscillator B is led to synchronous motor12 and to a switch 47, Fig. 3.

Asynchronous motor 2 may be connected to an alter.- nating currentvoltage source 48 by closing switch 49.

When voltage source 48 is in operation and switch v49 is, closed, theunit combination composed of motors 2 and 4 are set into operation andin the absence of watch ticks from 42, motor 2 operates in theneighborhood of 3050 revolutions per minute. When watch ticks from watch42 are set into use, the amplified pulsations of these ticks being, say,exactly 5 per second generate a generally sinusoidal frequency inoscillator B which in turn causes a load on the rotor of synchronousmotor 4 until it finally pulls it down to a speed of exactly 300revolutions per minute. At this time asynchronous motor 2 operates atexactly 10 times this speed or exactly 3,000 revolutions per minute. Ifswitch 50 is closed in the righthand direction on the highlystandardized alternating current source 51 and switch 52 is closedproviding driv-v ing power to asynchronous motor 1, synchronous motor 11giving maximum torque at 300 revolutions per minute causes motor 1 tooperate at exactly 3,000 revolutions per minute and an opposite magneticdrag on balance beam 28. Disks 23 and 24 (Fig. 1) cause pointer toindicate zero which means that watch 42 is ticking exactly the same rateas the frequency of source 51. If the ticks of'watch 42 exceed 5 persecond the magnetic drag on the beam 28 indicates fast on the scale 36and if the ticks of the watch 42 do not equal 5 per second, the drag onbeam 28 decreases some and the pointer indicates slow, which provides asupersensitive method of indicating the rates of going of a watchdirectly, which is visible to all concerned without the employment ofcharts or other special indicating apparatus which requires knowledgeand skill to understand.

The readings are immediate and no time is lost in making andinterpreting charts and similar devices.

If a standardized frequency source such as 51 is not available astandardized watch 53 may be employed to take its place at a much lessover all cost. Watch 53 has its tick-s transduced into electroniccurrent by microphone 53, which is fed into an amplifier C which may bean exact duplicate of the amplifier shown in dotted area A. Amplifier Coutput is fed into oscillator D which may be an exact duplicate of theoscillator shown in dotted area B. The output of oscillator D is fed tothe left hand set of contacts of switch which in turn connects it tosynchronous motor 11, controlling the speedof asynchronous motor 1 whichis driven by electronic current source 58 when switch 52 is closed. Whenswitch 50 is closed against its left hand contacts the operation of thedevice is exactly similar to the operation of the before describedconditions when switch 50 is closed against the right hand contactsoperating from standardized frequency source 51, the only differencebeing that the watch 53 and its connected circuit supplies thestandardized frequency instead of frequency source 51.

If switches 49 and 52 are closed and switch 50 is allowed to remain openand switch 47 is closed both synchronous control motors then operatefrom the same fre-.

quency source and under this condition balance beam 28';

7 than set it to some definite loss or some definite gain position.

' However, the markings on scale 36 can be drawn as accurately asdesired. Those skilled in the art will appreciate that this inventioncan be used in power plants to obtain the instantaneous frequency orspeeds that require close frequency control, by the employment of astandardized frequency source 51 instead of by the present method ofwaiting until the frequency again is suflicicut to be noticeable on aclock which may require some time.

The present invention provides a precision frequency meter for powerplants not obtainable by any indicating frequency instrument of theprior art.

Further and other applications are obvious to those skilled in the artto which the invention appertains.

Having described the objects and nature of this invention the noveltythereof is more clearly set forth in the appended claims.

I claim:

1. In an apparatus deriving time control signal energy from a source ofrelatively short duration periodic electrical impulses separated byeffectively zero energy relatively long time intervals jointly havingtime-controlled repetition frequency and providing instrument electricmotor shaft speeds supersynchronous with the two-pole synchronous motorspeed of said frequency, a source of timed frequency electrical signalimpulses separated by effectively zero energy time intervals, electrondischange tube circuit organization means converting said separatedsignal impulses into an alternating current having an effecivelyconinuous Wave form and a frequency identical with the repetitionfrequency of said impulses, a synchronous electric motor deriving usefultorque energy from said alternating current only at synchronousfrequency speed, an asynchronous electric motor having continuous torquethrough a wide range of speeds including a multiple speed of saidsynchronous frequency speed, a separate source of driving energy forsaid asynchronous motor, and rigid linkage mechanical gearing comprisinga toothed gear speed-multiplying power transmission coupling the shaftsof said motors to operate in exact timed relation to the periodicity ofsaid signal impulses.

2. In an apparatus deriving time control signal energy from a source ofrelatively short duration periodic electrical impulses separated byeffectively zero energy relatively long time intervals jointly havingtime-controlled repetition frequency and providing instrument electricmotor shaft speeds supersynchronous with the two-pole synchronous motorspeed of said frequency, a source of timed frequency electrical signalimpulses separated by effectively zero energy time intervals, saidfrequency being of a relatively low order, electron discharge tubecircuit organization means converting said separated signal impulsesinto an alternating current having an effectively continuous waveformand a frequency identical with the repetition frequency of saidimpulses, a synchronous electric motor deriving useful torque energyfrom said alternating current only at synchronous frequency speed,

4 ternating current,

an asynchronous electric motor having continuous torque through a Widerange of speeds including a multiple speed of said synchronous frequencyspeed, said multiple speed being of an order relatively high to thetwo-pole synchronous speed of said synchronous motor, a separate sourceof driving energy for said asynchronous motor, and rigid linkagemechanical gearing comprising a toothed gear speed-multiplyingpower-transmission coupling the shafts of said motors causing thecoupled speed of said motors to operate in exact timed relation to theperiodicity of said signal impulses.

3. In an apparatus deriving time control signal energy from a source ofrelatively short duration periodic electrical impulses separated byeffectively zero energy relatively long time intervals jointly havingtime-controled repetition frequency and providing instrument electricmotor shaft speeds supersynchronous with the twopole synchronous motorspeed of said frequency, a source of timed frequency electrical signalimpulses separated by effectively zero energy time intervals, saidfrequency being of the order of the beats per second of timepieces,electron discharge tube circuit organization means converting saidseparated signal impulses into an alternating current having aneffectively continuous waveform and a frequency identical with therepetition frequency of said impulses, a synchronous electric motorderiving useful torque energy from said alternating current only atsynchronous frequency speed, an asynchronous electric motor havingcontinuous torque through a wide range of speeds including a multiplespeed of said synchronous frequency speed, said multiple speed being ofan order of rotations per second suited to eddy current speedindicators, a separate source of driving energy for said asynchronousmotor, and rigid linkage mechanical gearing coupling the shafts of saidmotors causing the coupled speed of said motors to operate in exacttimed relation to the periodicity of said signal impulses.

4. In an apparatus deriving time control signal energy from a source ofrelatively short duration periodic electrical impulese separated byeffectively Zero energy relatively long time intervals jointly havingtime-controlled repetition frequency and providing instrument electricmotor shaft speeds supersynchronous with the two-pole synchronous motorspeed of said frequency, a source of timed frequency electrical signalimpulses separated by effectively zero energy time intervals, electrondischarge tube circuit organization means converting said separatedsignal impulses into an alternating current having an effectivelycontinuous waveform and a frequency identical with the repetitionfrequency of said impuls'es, a synchronous electric motor derivinguseful torque energy,

from said alternating current only at synchronous frequency speed, anasynchronous electric motor having continuous torque through a widerange of speeds including a multiple speed of said synchronous frequencyspeed, a separate source of driving energy for said asynchronous motor,rigid linkage mechanical gearing comprising a toothed gearspeed-multiplying power-transmission cou pling the shafts of saidmotors, and two said motors coupled forming an electromechanical filterreducing extraneous electrical organization oscillations about the meanfrequency of said timed impulses.

5. In an apparatus for converting periodic electrical impulses of arelatively low frequency into alternating currents and driving anelectric motor at shaft speeds supersynchronous to the two-polesynchronous motor speed of said low frequency, a source of periodicelectrical impulses, an electric motor operable at said supersynchronousspeed, electron discharge tube circuit organization means convertingsaid impulses into alsaid alternating current providing driving energyfor said motor, and said organization means including a toot edgearspeed-multiplying powertransmission including rigid linkageelectromechanical filter means reducing extraneous electricalorganization oscillations about the mean frequency of said electricalimpulses.

References Cited in the file of this patent UNITED STATES PATENTS1,686,638 Pierce Oct. 9, 1928 1,728,554 Knight Sept. 17, 1929 1,849,645Stoller Mar. 15, 1932 2,114,859 Schaelhlin Apr. 19, 1938 2,506,766Bartelink May 9, 1950 2,577,190 Hare Dec. 4, 1951 FOREIGN PATENTS196,402 Germany Mar. 12, 1908

